Detection of extragalactic CF+ toward PKS 1830−211 - Chemical differentiation in the absorbing gas

We report the first extragalactic detection of the fluoromethylidynium ion CF+ in the z = 0.89 absorber toward PKS 1830-211. We estimate an abundance of similar to 3 x 10(-10) relative to H-2 and that similar to 1% of fluorine is captured in CF+. The absorption line profile of CF+ is found to be markedly different from that of other species observed within the same tuning, and is notably anticorrelated with CH3OH. On the other hand, the CF+ profile resembles that of [CI]. Our results are consistent with expected fluorine chemistry and point to chemical differentiation in the column of absorbing gas.